Filled polymer composite and synthetic building material compositions

ABSTRACT

The invention relates to composite compositions having a matrix of polymer networks and dispersed phases of particulate or fibrous materials. The matrix is filled with a particulate phase, which can be selected from one or more of a variety of components, such as fly ash particles, axially oriented fibers, fabrics, chopped random fibers, mineral fibers, ground waste glass, granite dust, or other solid waste materials. A system for providing shape and/or surface features to a moldable material includes, in an exemplary embodiment, at least two first opposed flat endless belts spaced apart a first distance, with each having an inner surface and an outer surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/764,012, filed Jan. 23, 2004, currently pending, which is herebyincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to composite compositions having matrices ofpolymer networks and dispersed phases of particulate and/or fibrousmaterials, which have excellent mechanical properties, rendering themsuitable for use in load bearing applications, such as in buildingmaterials. The composites are stable to weathering, can be molded andcolored to desired functional and aesthetic characteristics, and areenvironmentally friendly, since they can make use of recycledparticulate or fibrous materials as the dispersed phase. The inventionrelates to methods and systems for imparting desired shape and surfacecharacteristics to a moldable or pliable material as the material curesor hardens. It is particularly applicable to the shaping and embossingof thermosetting resin systems during curing, and can be used to formthese resin systems into a variety of products, including syntheticlumber, roofing, and siding.

2. Description of the Related Art

Polymeric composite materials that contain organic or inorganic fillermaterials have become desirable for a variety of uses because of theirexcellent mechanical properties, weathering stability, and environmentalfriendliness.

These materials can be are relatively low density, due to their foaming,or high density when unfoamed, but are extremely strong, due to thereinforcing particles or fibers used throughout. Their polymer contentalso gives them good toughness (i.e., resistance to brittle fracture),and good resistance to degradation from weathering when they are exposedto the environment. This combination of properties renders somepolymeric composite materials very desirable for use in buildingmaterials, such as roofing materials, decorative or architecturalproducts, outdoor products, insulation panels, and the like.

In addition, the filler materials used need not be virgin materials, andcan desirably be recycled fibers or particulates formed as waste orby-product from industrial processes. Polymeric composites allow thesematerials to be advantageously reused, rather than present disposalproblems.

Filled composite polymeric materials have been described in U.S. Pat.Nos. 5,302,634; 5,369,147; 5,548,315; and 5,604,260, the contents ofeach of which is incorporated herein by reference. However, thematerials disclosed in these patents all use polyester polyurethaneresins that are formed as the reaction products of unsaturated polyesterpolyols, saturated polyols, poly- or di-isocyanates, and a reactivemonomer, such as styrene. The number of different reactants, and thecomplexity of the resulting process chemistry, adds increased cost tothe preparation of these materials, both through added costs formaterials inputs and through added capital costs for additional processequipment.

A filled closed cell foam material is disclosed in U.S. Pat. No.4,661,533 (Stobby), but provides much lower densities than are desirablefor structural building products. Moreover, Stobby does not disclose orsuggest a composite material that is “self-skinning,” i.e., that forms acontinuous skin on the surface of the material that covers and protectsthe material underneath, which is porous, and subject to visiblescratching.

Various techniques exist for continuously forming a soft or moldablematerial while it hardens or cures. For example, conveyor belts can beused to provide continuous support and movement for materials, and insome cases the belt faces may be contoured or profiled to mold thesurfaces of the material and to impart a shape, feature, or surfaceappearance to the material. Two or more such belts may be configured tooperate with the belt surfaces opposed and the material to be molded orshaped disposed between them. These systems can form fairly detailedthree-dimensional products.

However, when such systems are used to form a foamed product, thestructure of the overall system must be sufficiently strong to containthe pressure of the expanding foam. The longer the forming system andthe larger the cross-section of the product to be formed, the greaterthe total force due to pressure and friction that the system mustcontain and overcome. As a result, in general, belt systems have notbeen thought to be suitable for formation of resin systems that involvefoaming of the polymer matrix.

Forming systems have been developed to produce large rectangularpolyurethane foam buns; these systems typically contain the foamingmaterial within roller-supported films or sheets. The many rollers usedin these systems contain the increase in pressure due to foaming, andalso help to minimize system friction. However, these systems aregenerally not able to mold detail or texture into the product surface.

Pullers are two-belted machines designed to grip and pull an extrudedprofile. As indicated above, conventional two-belt systems, such aspullers that utilize thick profiled belts, may be configured tocontinuously mold detail and texture into a product. However, theseforming systems typically require profiled belts with relatively thicksidewall cross sections. The thick sidewalls minimize deflection of theunsupported sides of the mold-belt, thereby maintaining the intendedproduct shape, and limiting extrusion of material through the resultantgap between belts. The thickness of the product formed by a conventionaltwo-belt system is thus limited in practice by the thickness and widthof the profiled mold-belts. Thicker belts needed to form products withdeeper profiles require larger diameter end pulleys in order to preventexcessive bending, stretching, and premature breakage of the moldmaterial.

In addition, most pullers are relatively short (6 feet or less). Theseshort forming systems tend to require slower production speeds, allowingthe product enough time in-mold to harden sufficiently before exitingthe forming unit. Longer two-belt machines can be made, but in order tomanage belt/bed friction these longer systems typically require the useof rollers to support the back of the profiled belts. Roller supportedmold-belts tend to allow the mold faces to separate between rollerswhere the belts are unsupported, allowing material to leak between beltfaces.

To continuously mold larger foamed cross-sections and to impartirregular shape or surface detail to the product, table-top conveyorsare frequently used. Table-top conveyors use segmented metal moldsections attached to a metal chain-type conveyor. Two table-topconveyors are typically arranged face-to-face when used in this type ofapplication, providing a rigid continuous mold. Preventing material frommigrating into the joints between adjacent mold sections can beproblematic for this type of forming system and may required the use ofplastic films disposed between the mold and material to prevent leaks.In addition, such table-top conveyor systems are complex and costly.

Because of the various difficulties and deficiencies described above forexisting forming systems, there remains a need in the art for a low costforming system that can shape a curing polymer system, and in particulara foaming polymer system, without leaking. There is a need for such asystem that can impart surface patterns and designs to the curingmaterial, and that has sufficiently low friction and thickness that itcan be practically made long enough to allow sufficient curing time inthe system.

SUMMARY OF THE INVENTION

It has been found, however, that a highly filled, foamed or unfoamedcomposite polymeric material having good mechanical properties can beobtained without the need for all of the components required in thepatents cited above. This results in a substantial decrease in cost,because of decreased materials cost, and because of decreased complexityof the process chemistry, leading to decreased capital investment inprocess equipment.

In one embodiment, the invention relates to composite compositionshaving a matrix of polymer networks and dispersed phases of particulateor fibrous materials. The polymer matrix contains a polyurethane networkformed by the reaction of a poly- or di-isocyanate and one or moresaturated polyether or polyester polyols, and an optionalpolyisocyanurate network formed by the reaction of optionally addedwater and isocyanate. The matrix is filled with a particulate phase,which can be selected from one or more of a variety of components, suchas fly ash particles, axially oriented fibers, fabrics, chopped randomfibers, mineral fibers, ground waste glass, granite dust, or other solidwaste materials. The addition of water can also serve to provide ablowing agent to the reaction mixture, resulting in a foamed structure,if such is desired.

The composite material of the invention is advantageously used asstructural building material, and in particular as synthetic lumber, forseveral reasons. First, it has the desired density, even when foamed, toprovide structural stability and strength. Second, the composition ofthe material can be easily tuned to modify its properties by, e.g.,adding oriented fibers to increase flexural stiffness, or by addingpigment or dyes to hide the effects of scratches. This can be done evenafter the material has been extruded. Third, the material isself-skinning, forming a tough, slightly porous layer that covers andprotects the more porous material beneath. This tough, continuous,highly adherent skin provides excellent water and scratch resistance. Inaddition, as the skin is forming, an ornamental pattern (e.g., asimulated wood grain) can be impressed on it, increasing the commercialacceptability of products made from the composite.

In a more specific embodiment, the invention relates to a polymer matrixcomposite material, comprising:

(1) a polyurethane formed by reaction of

-   -   (a) one or more monomeric or oligomeric poly- or di-isocyanates;    -   (b) a first polyether polyol having a first molecular weight;        and    -   (c) an optional second polyether polyol having a second        molecular weight lower than the first molecular weight; and

(2) optionally, a polyisocyanurate formed by reaction of a monomeric oroligomeric poly- or di-isocyanate with water or other blowing agents;

(3) a particulate inorganic filler.

As indicated above, the polymer matrix composite material of theinvention can have a variety of different uses. However, it isparticularly suitable in structural applications, and in particular asan synthetic lumber. Accordingly, another specific embodiment of theinvention relates to an synthetic lumber, comprising the polymer matrixcomposite material described above, and having a relatively porousmaterial and a relatively non-porous toughening layer disposed on andadhered to the porous material.

It has been found that the process used to manufacture the polymermatrix composite material and the synthetic lumber formed therefrom canhave an important impact on the appearance and properties of theresulting material, and thus on its commercial acceptability.Accordingly, another particular embodiment of the invention relates to amethod of producing a polymer matrix composite, by:

(1) mixing a first polyether polyol having a first molecular weight anda second polyether polyol having a second molecular weight higher thanthe first molecular weight with a catalyst, optional water, and optionalsurfactant;

(2) optionally introducing reinforcing fibrous materials into themixture;

(3) introducing inorganic filler into the mixture;

(4) introducing poly- or di-isocyanate into the mixture; and

(5) allowing the exothermic reaction to proceed without forced coolingexcept to control runaway exotherm.

The materials of the invention, and the process for their preparation,are environmentally friendly. They provide a mechanism for reuse ofparticulate waste in a higher valued use, as described above. Inaddition, the process for making them optionally uses water in theformation of polyisocyanurate, which releases carbon dioxide as theblowing agent. The process thus avoids the use of environmentallyharmful blowing agents, such as halogenated hydrocarbons.

The invention disclosed in this application is a new type of formingsystem utilizing up to six belts. The forming system is uniquely suitedto the continuous forming of a range of product sizes with intricatemolded-in detail. Material that may be formed using the described systeminclude but are not limited to: thermoplastic and thermoset plasticcompounds, highly-filled plastic compounds, elastomers, ceramicmaterials, and cementitious materials. The system is particularly suitedto the forming of foamed materials. The material to be formed may bepoured, dropped, extruded, spread, or sprayed onto or into the formingsystem.

In one embodiment, the invention relates to a system for providingshape, surface features, or both, to a moldable material, the systemhaving:

at least two first opposed flat endless belts disposed a first distanceapart from each other, each having an inner surface and an outersurface;

at least two second opposed flat endless belts disposed substantiallyorthogonal to the first two opposed endless belts and a second distanceapart from each other, and each having an inner surface and an outersurface;

a mold cavity defined at least in part by the inner surfaces of at leasttwo of the opposed flat endless belts; and

a drive mechanism for imparting motion to at least two of the opposedflat endless belts.

In a more particular embodiment, the invention relates to a formingsystem having 4 flat belted conveyors configured so as to define andenclose the top, bottom, and sides of a 4-sided, open-ended channel, andan additional two profiled mold-belts that are configured to fit snugly,face-to-face within the channel provided by the surrounding flat belts.All belts are endless and supported by pulleys at the ends of theirrespective beds so as to allow each belt to travel continuously aboutits fixed path.

In another embodiment, the invention relates to a method of continuouslyforming a moldable material to have a desired shape or surface featureor both, comprising:

introducing the moldable material into an end of a mold cavity formed atleast in part by the inner surfaces of two substantially orthogonal setsof opposed flat belts;

exerting pressure on the moldable material through the opposed flatbelts;

transferring the moldable material along the mold cavity by longitudinalmovement of the belts;

after sufficient time for the material to cure or harden into the moldedconfiguration and thereby form molded material, removing the moldedmaterial from the mold cavity.

The system and method are versatile, permitting the production of arange of product sizes and profiles using the same machine. In anexemplary embodiment, the system and method provide for the continuousforming of synthetic lumber, roofing tiles, molded trim profiles, sidingor other building products from heavily-filled, foamed thermoset plasticcompounds and/or foamed ceramic compounds with organic binders.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a top plan view, FIG. 1B is a side plan view, and FIG. 1C isan end plan view of one embodiment of a system of the invention.

FIG. 2 is a partially expanded isometric view of one end of the systemillustrated in FIG. 1.

FIG. 3A is an end plan view of one embodiment of the system of theinvention. FIG. 3B is an exploded sectional view of the system of FIG.3A.

FIG. 4 is a sectional view of a profile mold belt used in certainembodiments of the system of the invention.

FIG. 5 is a partial sectional, partial end plan view of a four beltconfiguration of the system of the invention.

FIG. 6 is a sectional view of a configuration of the system of theinvention using drive belts and supporting the sides of the mold beltswith pressurized air.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As described above, one embodiment of the invention relates to acomposite composition containing a polymeric matrix phase and adispersed inorganic particulate phase, and which can contain othermaterials, such as reinforcing fibers, pigments and dyes, and the like.One of the desirable properties of the material is its self-skinningnature.

The polymeric phase desirably contains at least a polyurethane,generally considered to be a 2-part or thermosetting polyurethane. Thepolyurethane is formed by reacting a poly- or di-isocyanate (hereinafter“isocyanate”), particularly an aromatic diisocyanate, more particularly,a methylene diphenyl diisocyanate (MDI), with one or more polyetherpolyols, described in more detail below.

The MDI used in the invention can be MDI monomer, MDI oligomer, or amixture thereof. The particular MDI used can be selected based on thedesired overall properties, such as the amount of foaming, strength ofbonding to the inorganic particulates, wetting of the inorganicparticulates in the reaction mixture, strength of the resultingcomposite material, and stiffness (elastic modulus). Although toluenediisocyanate can be used, MDI is generally preferable due to its lowervolatility and lower toxicity. Other factors that influence theparticular MDI or MDI mixture used in the invention are viscosity (a lowviscosity is desirable from an ease of handling standpoint), cost,volatility, reactivity, and content of 2,4 isomer. Color may be asignificant factor for some applications, but does not generally affectselection of an MDI for preparing synthetic lumber.

Light stability is also not a particular concern for selecting MDI foruse in the composite of the invention. In fact, the composite of theinvention allows the use of isocyanate mixtures not generally regardedas suitable for outdoor use, because of their limited light stability.When used in the composite of the invention, these materialssurprisingly exhibit excellent light stability, with little or noyellowing or chalking. Since isocyanate mixtures normally regarded assuitable for outdoor use (generally aliphatic isocyanates) areconsiderably more expensive than those used in this invention, theability of the invention to use MDI mixtures represents a significantcost advantage.

Suitable MDI compositions for use in the invention include those havingviscosities ranging from about 25 to about 200 cp at 25° C. and NCOcontents ranging from about 30% to about 35%. Generally, isocyanates areused that provide at least 1 equivalent NCO group to 1 equivalent OHgroup from the polyols, desirably with about 5% to about 10% excess NCOgroups. Suitable isocyanates include Bayer MRS-4, Bayer MR Light, DowPAPI 27, Bayer MR5, Bayer MRS-2, and Rubinate 9415.

As indicated above, the isocyanate used in the invention is reacted withone or more polyols. In general, the ratio of isocyanate to polyol,based on equivalent weights (OH groups for polyols and NCO groups forisocyanates) is generally in the range of about 0.5:1 to about 1.5:1,more particularly from about 0.8:1 to about 1.1:1. Ratios in theseranges provide good foaming and bonding to inorganic particulates, andyields low water pickup, fiber bonding, heat distortion resistance, andcreep resistance properties. However, precise selection of the desiredratio will be affected by the amount of water in the system, includingwater added per se as a foaming agent, and water introduced with othercomponents as an “impurity.”

The polyol or polyols used may be single monomers, oligomers, or blends.Mixtures of polyols can be used to influence or control the propertiesof the resulting polymer network. For example, mixtures of two polyols,one a low molecular weight, rubbery (relative to the second) polyol andthe other a higher molecular weight, more rigid (relative to the first)polyol. The amount of rigid polyol is carefully controlled in order toavoid making the composite too brittle (a ratio of flexible polyol torigid polyol of between about 5 wt % and about 20 wt %, moreparticularly around 15 wt % has generally been found to be suitable. Itis generally desirable to use polyols in liquid form, and generally inthe lowest viscosity liquid form available, as these can be more easilymixed with the inorganic particulate material. So-called “EO” tippedpolyols can be used; however their use is generally avoided where it isdesired to avoid “frosting” of the polymer material when exposed towater.

In general, desirable polyols include polyether polyols, such asMULTRANOL (Bayer), including MULTRANOL 3400 or MULTRANOL 4035, ethyleneglycol, diethylene glycol, triethylene glycol, dipropylene glycol,glycerol, 2-butyn-1,4-diol, neopentyl glycol, 1,2-propanediol,pentaerythritol, mannitol, 1,6-hexanediol, 1,3-buytylene glycol,hydrogenated bisphenol A, polytetramethyleneglycolethers,polythioethers, and other di- and multi-functional polyethers andpolyester polyethers, and mixtures thereof. The polyols need not bemiscible, but should not cause compatibility problems in the polymericcomposite.

As indicated above, the composite of the invention can desirably beprepared by mixing the polyols together (if multiple polyols are used),and then mixing them with various additives, such as catalysts,surfactants, and foaming agent, and then adding the inorganicparticulate phase, then any reinforcing fiber, and finally theisocyanate.

One or more catalysts are generally added to control the curing time ofthe polymer matrix (upon addition of the isocyanate), and these may beselected from among those known to initiate reaction between isocyanatesand polyols, such as amine-containing catalysts, such as DABCO andtetramethylbutanediamine, tin-, mercury- and bismuth-containingcatalysts. To increase uniformity and rapidity of cure, it may bedesirable to add multiple catalysts, including a catalyst that providesoverall curing via gelation, and another that provides rapid surfacecuring to form a skin and eliminate tackiness. For example, a liquidmixture of 1 part tin-containing catalyst to 10 parts amine-containingcatalyst can be added in an amount greater than 0 wt % and below about0.10 wt % (based on the total reaction mixture) or less, depending onthe length of curing time desired. Too much catalyst can result inovercuring, which could cause buildup of cured material on theprocessing equipment, or too stiff a material which cannot be properlyshaped, or scorching; in severe cases, this can lead to unsaleableproduct or fire. Curing times generally range from about 5 seconds toabout 2 hours.

A surfactant may optionally be added to the polyol mixture to functionas a wetting agent and assist in mixing of the inorganic particulatematerial. The surfactant also stabilizes bubbles formed during foaming(if a foamed product is desired) and passivates the surface of theinorganic particulates, so that the polymeric matrix covers and bonds toa higher surface area. Surfactants can be used in amounts below about0.5 wt %, desirably about 0.3 wt %, based on the total weight of themixture. Excess amount of surfactant can lead to excess waterabsorption, which can lead to freeze/thaw damage to the compositematerial. Silicone surfactants have been found to be suitable for use inthe invention. Examples include DC-197 and DC-193 (silicone-based, AirProducts), and other nonpolar and polar (anionic and cationic) products.

Foaming agent may also be added to the polyol mixture if a foamedproduct is desired. While these may include organic blowing agents, suchas halogenated hydrocarbons, hexanes, and other materials that vaporizewhen heated by the polyol-isocyanate reaction, it has been found thatwater is much less expensive, and reacts with isocyanate to yield CO₂,which is inert, safe, and need not be scrubbed from the process. Equallyas important, CO₂ provides the type of polyurethane cells desirable in afoamed product (i.e., mostly open, but some closed cells), is highlycompatible with the use of most inorganic particulate fillers,particularly at high filler levels, and is compatible with the use ofreinforcing fibers. Other foaming agents will not produce the same foamstructure as is obtained with water.

If water is not added to the composition, some foaming may still occurdue to the presence of small quantities of water (around 0.2 wt %, basedon the total weight of the reaction mixture) introduced with the othercomponents as an “impurity.” On the other hand, excessive foamingresulting from the addition of too much water (either directly orthrough the introduction of “wet” reactants or inorganic particulatematerials) can be controlled by addition of an absorbent, such as UOP“T” powder.

The amount of water present in the system will have an important effecton the density of the resulting composite material. This amountgenerally ranges from about 0.10 wt % to about 0.40 wt %, based on theweight of polyol added, for composite densities ranging from about 20lb/ft³ to about 90 lb/ft³.

Reinforcing fibers can also be introduced into the polyol mixture priorto introduction of the isocyanate. These can include fibers per se, suchas chopped fiberglass, or fabrics or portions of fabrics, such asrovings or linear tows, or combinations of these. Typically, thereinforcing fibers range from about 0.125 in. to about 1 in, moreparticularly from about 0.25 in to about 0.5 in. The reinforcing fibersgive the material added strength (flexural, tensile, and compressive),increase its stiffness, and provide increased toughness (impact strengthor resistance to brittle fracture). Fabrics, rovings, or tows increaseflexural stiffness and creep resistance. The inclusion of the particularpolyurethane networks of the invention, together with the optionalsurfactants, and the inorganic particulate sizes used make the compositeof the invention particularly and surprisingly well suited for inclusionof reinforcing fibers in foamed material, which normally would beexpected to rupture or distort the foam bubbles and decrease thestrength of the composite system.

In addition to inclusion of reinforcing fibers into the polyol mixtureprior to polymerization, oriented axial fibers can also be introducedinto the composite after extrusion, as the polymer exits the extruderand prior to any molding. The fibers (e.g., glass strings) can desirablybe wetted with a mixture of polyol (typically a higher molecular weight,rigid polyol) and isocyanate, but without catalyst or with a slow curecatalyst, or with other rigid or thermosetting resins, such as epoxies.This allows the wetted fiber to be incorporated into the compositebefore the newly added materials can cure, and allows this curing to bedriven by the exotherm of the already curing polymer in the bulkmaterial.

Whether added before or after polymerization and extrusion, thecomposite material of the invention contains a polymeric matrix phasethat is strongly bonded to the dispersed reinforcing fibers, increasingthe strength and stiffness of the resulting material. This enables thematerial to be used as a structural synthetic lumber, even at relativelylow densities (e.g., about 20 to about 60 lb/ft³).

Pigment or dye can be added to the polyol mixture or can be added atother points in the process. The pigment is optional, but can help makethe composite material more commercially acceptable, more distinctive,and help to hide any scratches that might form in the surface of thematerial. Typical examples of pigments include iron oxide, typicallyadded in amounts ranging from about 2 wt % to about 7 wt %, based on thetotal weight of the reaction mixture.

The inorganic particulate phase is an important feature of theinvention, and is typically present in amounts ranging between about 45wt % to about 85 wt % of the total composition. Increasing theproportion of inorganic particulate can lead to increased difficulty inmixing, making the inclusion of a surfactant more desirable. Theinorganic particulate material should have less than about 0.5 wt %water (based on the weight of the particulate material) in order toavoid excessive or uncontrolled foaming.

It is generally desirable to use particulate materials with a broadparticle size distribution, because this provides better particulatepacking, leading to increased density and decreased resin level per unitweight of composite. Since the inorganic particulate is typically someform of waste or scrap material, this leads to decreased raw materialcost as well. Particles having size distributions ranging from about0.0625 in to below 325 mesh have been found to be particularly suitable

Suitable inorganic particulates can include ground glass particles, flyash, bottom ash, sand, granite dust, and the like, as well as mixturesof these. Fly ash is desirable because it is uniform in consistency,contains some carbon (which can provide some desirable weatheringproperties to the product due to the inclusion of fine carbon particleswhich are known to provide weathering protection to plastics, and theeffect of opaque ash particles which block UV light, and contains somemetallic species, such as metal oxides, which are believed to provideadditional catalysis of the polymerization reactions. Ground glass (suchas window or bottle glass) absorbs less resin, decreasing the cost ofthe composite. A 1:1 mixture of coal fly ash and bottom ash has alsobeen found to be suitable as the inorganic particulate composition. Ingeneral, fly ash having very low bulk density (e.g., less than about 40lb/ft³) and/or high carbon contents (e.g., around 20 wt % or higher) areless suitable, since they are more difficult to incorporate into theresin system, and may require additional inorganic fillers that havemuch less carbon, such as foundry sand, to be added. Fly ash produced bycoal-fueled power plants, including Houston Lighting and Power powerplants, fly and bottom ash from Southern California Edison plants(Navajo or Mohave), fly ash from Scottish Power/Jim Bridger power plantin Wyoming, and fly ash from Central Hudson Power plant have been foundto be suitable for use in the invention.

The process for producing the composite material may be operated in abatch, semibatch, or continuous manner. Mixing may be conducted usingconventional mixers, such as Banbury type mixers, stirred tanks, and thelike, or may be conducted in an extruder, such as a twin screw,co-rotating extruder. When an extruder is used, additional heating isgenerally not necessary, especially if liquid polyols are used. Inaddition, forced cooling is not generally required, except for minimalcooling to control excessive or runaway exotherms.

For example, a multi-zone extruder can be used, with polyols andadditives introduced into the first zone, inorganic particulatesintroduced in the second zone, and chopped fibers, isocyanate, andpigments introduced in the fifth zone. A twin screw, co-rotating,extruder (e.g. 100 mm diameter, although the diameter can be variedsubstantially) can be used, with only water cooling (to maintain roomtemperature), and without extruder vacuum (except for ash dust). Liquidmaterials can be pumped into the extruder, while solids can be added bysuitable hopper/screw feeder arrangements. Internal pressure build up insuch an exemplary arrangement is not significant.

Although gelation occurs essentially immediately, complete curing cantake as long as 48 hours, and it is therefore desirable to wait at leastthat long before assessing the mechanical properties of the composite,in order to allow both the composition and the properties to stabilize.

As explained above, the composite material of the invention isadvantageously used in structural products, including synthetic lumber.The synthetic lumber may be formed in a batch, semibatch, or continuousfashion. For example, in continuous operation, polymerized (andpolymerizing) material leaving the extruder (after optionalincorporation of post-extruder fibers, tows, or rovings) is supplied toa forming system, which provides dimensional constraint to the material,and can be used to pattern the surfaces of the resulting syntheticlumber with simulated woodgrain or other designs, in order to make thematerial more commercially desirable. For example, a conveyor beltsystem comprising 2, 4, or 6 belts made from a flexible resin havingwood grain or other design molded therein can be used. One such suitablesystem is described in copending U.S. patent application Ser. No.10/764,013, filed on even date herewith, the entire contents of whichare incorporated herein by reference. Desirably, the belts are formedfrom a self-releasing rubber or elastomeric material so that it will notadhere to the polymer composite. Suitable belt materials includesilicone rubber, oil impregnated polyurethane, or synthetic or naturalrubbers, if necessary coated with a release agent, such as waxes,silicones, or fluoropolymers.

For clarity of understanding, the invention will be described hereinwith respect to a single apparatus. It should be understood, however,that the invention is not so limited, and the system and method of theinvention may involve two or more such systems operated in series or inparallel, and that a single system may contain multiple sets of belts,again operated in series or in parallel.

Flat-Belted Conveyor Channel

Each set of opposed flat belt conveyors are oriented so that theirbearing surfaces face each other. One set of opposed flat belts can bethought of as “upper” and “lower” belts, although these descriptors arenot limiting, nor do they require that the two opposed belts behorizontal. In practice, however, one set of opposed belts (the upperand lower belts) will be substantially horizontal. These belts candefine the upper and lower surfaces of a mold cavity (when the device isoperated in four-belt mode), or may provide support and drive surfacesfor a set of opposed profile mold belts (when the device is operated insix-belt mode). The remaining set of opposed flat belts are disposedsubstantially orthogonal to the first set. As used herein, the term“substantially orthogonal” means close to perpendicular, but allowingfor some deviation from 90° resulting from adjustment of the device,variations from level in the manufacturing floor, etc. Thissubstantially orthogonal arrangement is accomplished in two basicconfigurations.

The first exemplary configuration involves disposing the flat bearingsurfaces of the second set of belts along the sides of the space formedby the first set of belts, thereby forming an open-ended mold cavitythat is enclosed by flat belts, and having a length corresponding to thelength of the “side” belts. This configuration is illustrated in FIG. 5.FIG. 1A provides a top view, FIG. 1B a side view, and FIG. 1C an endview, of a system 2 having upper flat belt 4, lower flat belt 4′ upperprofile mold belt 6, lower profile mold belt 6′, and side belts 8 and8′. These side belts extend longitudinally approximately the samedistance as the upper and lower flat belts, providing a mold cavity thatis supported from the side over virtually the entire length of theprofile mold belts. Profile mold belts 6 and 6′ are maintained intension by tensioning rolls 10. Flat belts 4 and 4′ are powered bydriven rollers 12 and 12′.

The arrangement of belts and the corresponding rollers for thisexemplary configuration can be seen in more detail in FIG. 2, which is apartially expanded view, wherein the upper flat belt 4, upper profilemold belt 6, and corresponding supports and rollers 10 and 12, have beenlifted away from the remainder of the system for ease of visualization.Side belts 8, 8′ are supported by side belt supports 14 and 14′, and canrun on side belt support rollers 16, 16′. These side belt supportrollers are powered, or unpowered, as illustrated in FIG. 2. Inaddition, upper and lower flat belts 4 and 4′ are supported by rigidsupporting surfaces, such as platens 18, 18′.

As mentioned above, each flat belt is supported by a slider-bed orplaten comprised of a rigid metal plate or other rigid supportingsurface, if the length of the belt makes such support necessary ordesirable. Generally, in order to provide sufficient curing time forfilled polyurethane foams, a support surface is desirable but notrequired. The surface of the slider-bed in one embodiment has a slipperycoating or bed-plate material attached or bonded to it (for example,ultra-high molecular weight polyethylene, PTFE, or other fluoropolymer).Also, the belt has a slippery backing material (for example, ultra-highmolecular weight polyethylene, PTFE or other fluoropolymer) to reducefriction between the bed and moving belt in an exemplary embodiment.

To further reduce friction and enhance cooling of the belts and conveyormachinery, the slider-beds and attached slippery surface material of aconveyor has a plurality of relatively small holes drilled through thesurface. These holes are in fluid communication with a source ofcompressed gas, such as air. As an example, a plenum chamber is providedbehind each slider bed, which is then connected to a source ofpressurized air. Pressurized air fed into each plenum passes through theholes in the bed, and provides a layer of air between the bed and theadjacent belt. This air film provides lubrication between the bed andadjacent belt as shown in FIG. 2., where compressed air is supplied tothe plenums through openings 20, 20′. The air fed into the plenums has apressure higher than the foaming pressure of the product to be useful inreducing operating friction. In one embodiment, shop air orhigh-pressure blowers are used to provide the pressurized air to feedthe plenums.

In a more particular exemplary embodiment, shown in FIG. 6, air supplyplenums are also used to provide support to the sides of the mold belts,either directly (shown) or through side belts (not shown). In FIG. 6,flat belts 4 and 4′ are supported by upper and lower air supply plenums32 and 32′, respectively. Areas of contact between the belts and theplenums are prepared from or coated with a low-friction substance, suchas PTFE, or are lubricated to lower the friction between the belts andthe supporting surfaces. Pressurized air 34 is supplied to these plenumsthrough openings 36, 36′, and exits the plenums through openings 38,38′, where it flows under and supports flat belts 4, 4′, which in turnsupport the upper and lower surfaces of profile mold belts 6, 6′. Inaddition, pressurized air 40 enters side plenums 42, 42′ throughopenings 44, 44′. The air leaves these side plenums through opening 46,46′, and flows against and supports the sides of profile mold belts 6,6′. This support can result either from the air flow impinging directlyon the sides of the mold belts, or from air flow impinging on thesurfaces of side belts that in turn press against the sides of theprofile mold belts. The profile mold belts, in turn, provide support tothe material being formed, 48.

The flat-belts are powered and driven at matching speeds with respect toone another. The matched speed are achieved, in one embodiment, bymechanical linkage between the conveyors or by electronic gearing of therespective motors. Alternatively, as illustrated in FIGS. 1 and 2, onlytwo flat belts are driven (for example, the two opposing belts withgreater contact area, which are typically the upper and lower belts)with the remaining two flat belts (for example, the side belts)un-driven and idling. The flat-belts form a relatively rigid movingchannel through which contoured mold-belts and/or forming product ismoved and contained.

The driven flat-belts utilize known driven roller technologies,including center-drive pulley mechanisms, whereby more than 180° ofcontact is maintained between each conveyor's driving pulley and belt,increasing the amount of force that may be delivered to the belt.

In another exemplary configuration, the side flat belts are disposedsubstantially orthogonal relative to the upper and lower flat belts suchthat their bearing surfaces face each other, and are in a planesubstantially perpendicular to the plane of the bearing surfaces of theupper and lower belts, as illustrated in FIG. 3. FIG. 3A is an end viewwith the corresponding drive and support apparatus removed for ease ofviewing. FIG. 3A shows side flat belts 8 and 8′ disposed between upperflat belt 4 and lower flat belt 4′. An expanded sectional view of thisexemplary configuration is provided in FIG. 3B. The frames 22 and 22′supporting the side belts are restrained in such a way as to allow theposition of the side flat belts to be adjusted laterally providing thedesired degree of pressure against the sides of profile mold belts 6 and6′ or to accommodate mold belts of alternate widths. This configurationprovides a relatively short, but highly contained mold cavity 24.

Mold-Belts

The contoured mold-belts are relatively thick belts with a rubbery facematerial attached to a fiber-reinforced backing or carcass as shown inFIG. 4. The profile mold belt 6′ is constructed to contain an innersurface 25, that defines part of mold cavity 24. It also has sidesurfaces 26, which contact side flat belts 8, 8′, and outer surface 30,which contacts the inner surface of flat belt 4′. Thefiber-reinforcement 28 in the backing of the belts will provide thestrength and rigidity in the belt while the face material has theprofile, surface features, and texture that is molded into the product.The desired mold profile, surface features, and texture are machined,cut, bonded, and/or cast into the surface of the mold-belts. The moldcavity created by the mold belts has a constant, irregular, and/orsegmented cross section. Multiple cavities can be incorporated into asingle set of mold belts. Suitable mold surface materials include, butare not restricted to Nitrile, Neoprene, polyurethane, siliconeelastomers, and combinations thereof. Suitable fibers for reinforcingthe profile mold belt include cotton, aramid, polyester, nylon, andcombinations thereof.

Each profile mold-belt travels beyond the ends of the surroundingflat-belt conveyors to a separate set of large pulleys or rollers thatmaintain tension and the relative position of each belt. In oneembodiment, the mold-belts are un-powered, functioning as idlers orslave belts to the powered flat belts behind them. In anotherembodiment, the mold belts are separately powered.

The temperature of the mold belts can be adjusted during production inthe event that additional heat is needed or surplus heat is to beremoved. If the temperature of the belt surface is adjusted, temperaturecontrolled air is blown onto the belt surfaces as the belts exit theflat-belted conveyor enclosure and follow their return path to theentrance of the forming machine. In one embodiment, infrared or otherradiant heaters are used to increase the temperature of the moldsurface. In another embodiment, temperature controlled air or otherfluid is routed through the conveyor frames to maintain predeterminedprocess temperatures.

Orientation

As described above, the exemplary orientation of the forming system isfor the contact surface between mold-belts to be horizontal. The gapbetween the upper and lower flat-belted conveyors (those conveyorsadjacent to the backs of the mold-belts), can be precisely maintainedsuch that the pair of mold-belts pass between them without being allowedto separate (presenting a gap to the molding material) and withoutexcessively compressing the mold-belt shoulders or side walls. In theexemplary embodiment, the upper conveyor is removable while not inoperation in order to permit replacement of the mold belts.

Side Conveyors

The flat-belted conveyors adjacent to the sides of the profile moldbelts provide structural support for the sides of the mold cavity,resist any deflection of the sides due to foaming pressure, and maintainalignment of the mold-belts. These side-supporting conveyors permit theuse of thinner mold-belt sidewalls, which reduces the cost and mass ofthe mold-belts. The use of these side-supporting conveyors also permitsthe molding of deeper product cross sections without requiring excessivemold-belt widths.

System Versatility

An exemplary configuration for the flat-belted conveyors is for the topand bottom conveyors to be wide, with the side conveyors sized to fitbetween the belts of the upper and lower conveyors in such a way thatthe surface of the upper and lower (wide) belts approach or make contactwith the edges of the side belts. The frames, pulleys, and slider-bedsof the side conveyors are slightly narrower than their respective beltsto avoid contact with the upper and lower belts. A cross section of thisexemplary configuration is shown in FIG. 3B as described above. Withthis orientation, the gap between the side conveyors is adjustable inorder to accommodate wider or narrower pairs of mold-belts. Thisconfiguration permits a range of product widths to be produced by thesame forming machine. Only the mold-belt set is replaced in order toproduce product of a different width.

To further increase the versatility of the forming machine, the sideconveyor belts, pulleys, and slider beds are replaced with taller orshorter components and the gap between upper and lower conveyorsadjusted accordingly. This feature permits the forming machine toaccommodate mold-belts of various depths to produce thicker or thinnercross sections.

Four-Belt Mode

The specific exemplary embodiments described above with respect to thedrawings generally relate to configuration of the system in “six beltmode.” In other words, an upper and lower flat belt, two side flatbelts, and an upper and lower profile mold belt. The mold belts permitsurface details, corner radii, irregular thicknesses, and deeper surfacetexture to be molded into the continuously formed product. However, forrectangular or square cross-sectioned products that do not requirecorner radii, deep texture, or localized features, the forming system isused without mold-belts, and operated in “four belt mode.” In thisexemplary operating configuration the four flat belts make directcontact with the moldable product and permits the product to form withinthe flat-sided cavity. When the forming system is used in thisconfiguration it is important that the upper and lower belts maintaincontact with the edges of the side belts to prevent seepage of thematerial between adjacent belts. In order to produce thicker or thinnerproducts in “four belt mode” the side flat belts, adjacent slider beds,and side belt pulleys are replaced with components in the targetthickness. The gap between side belts is adjusted to accommodate thetarget width. Using this approach a large variety of four-sidedcross-sections can be produced by the same machine without the addedcost of dedicated mold-belts.

The four belt configuration is illustrated in FIG. 5. The sectionalportion of the drawing shows that the mold cavity 24 is formed by thesurfaces of upper and lower flat belts 4, 4′ and the surfaces of sidebelts 8, 8′.

Fabrication

The forming system structure may be fabricated using metal materials andtypical metal forming and fabricating methods such as welding, bending,machining, and mechanical assembly.

The forming system is used to form a wide variety of moldable materials,and has been found to be particularly suitable for forming syntheticlumber.

Representative suitable compositional ranges for synthetic lumber, inpercent based on the total composite composition, are provided below:Rigid polyol about 6 to about 18 wt % Flexible polyol 0 to about 10 wt %Surfactant about 0.2 to about 0.5 wt % Skin forming catalyst about 0.002to about 0.01 wt % Gelation catalyst about 0.02 to about 0.1 wt % Water0 to about 0.5 wt % Chopped fiberglass 0 to about 10 wt % Pigments 0 toabout 6 wt % Inorganic particulates about 60 to about 85 wt % Isocyanateabout 6 to about 20 wt % Axial tows 0 to about 6 wt %.

The invention can be further understood by reference to the followingnon-limiting examples.

Example 1

A polymer composite composition was prepared by introducing 9.5 wt %rigid polyol (MULTRANOL 4035, Bayer), 0.3 wt % rubber polyol (ARCOLLG-56, Bayer), 0.3 wt % surfactant/wetting agent (DC-197, Air Products),0.005 wt % film forming organic tin catalyst (UL-28/22, Air Products),0.03 wt % amine gelation catalyst (33LV, Air Products), and 0.05 wt %water as foaming agent to the drive end of a 100 mm diameter twin screwco-rotating extruder with water cooling to maintain room temperature. Ata point around 60% of the length of the extruder, 4.2 wt % chopped glassfibers (Owens Corning) with ¼ to ½ inch lengths were added, along with4.0 wt % brown pigment (Interstar), 74 wt % fly ash (ISG), and 9.6 wt %isocyanate (MONDUR MR Light, Bayer). The extruder was operated at roomtemperature (75° F.), at 200 rpm for one hour. Following extrusion, 0.4wt % of a resin mixture of rubbery polyol (ARCOL LG-56, Bayer), andisocyanate (MONDUR MR Light, Bayer) were added to the surface of theextruded material to provide a bonding adhesive for glass tows. Theglass tows (Owens Corning) ¼ to ½ inch length were added in an amount ofaround 2 wt % to provide added rigidity, and were added just below thesurface of the material produced by the extruder.

The resulting composite material was particularly useful as syntheticdecking material.

Example 2

In a batch reactor, 16.4 wt % rigid polyol (Bayer 4035) was combinedwith 1.9 wt % flexible polyol (Bayer 3900), 0.2 wt % surfactant(DC-197), water, 3.2 wt % pigments, 0.0001 wt % UL-28 organic tincatalyst, and 0.1 wt % 33LV amine catalyst, and thoroughly mixed for 1minute. 31.5 wt % Wyoming fly ash was then added and mixed for anadditional 1 minute. Finally, 17.3 wt % isocyanate (1468A, Hehr), 0.9 wt% chopped brown fiber, 3.5 wt % chopped glass (0.25 in. diameter), andan additional 25.2 wt % Wyoming fly ash were added and mixed for 30seconds. The resulting material had a resin content of 36%, a ratio ofrigid to rubbery polyol of 90%, a solids content of 64%, a 10% excessisocyanate content, and a fiber content of 4.4%, all by weight based onthe total composition unless noted otherwise. The resulting material wassuitable for forming synthetic lumber boards.

Example 3

In a batch reactor, 16.4 wt % rigid polyol (Bayer 4035) was combinedwith 1.9 wt % flexible polyol (Bayer 3900), 0.2 wt % surfactant(DC-197), water, 3.2 wt % pigments, 3.5 wt % chopped glass (0.25 in.diameter), around 0.4 wt % Mohave bottom ash, 0.0001 wt % UL-28 organictin catalyst, and 0.1 wt % 33LV amine catalyst, and thoroughly mixed for1 minute. 31.5 wt % Wyoming fly ash was then added and mixed for anadditional 1 minute. Finally, 17.3 wt % isocyanate (1468A, Hehr), 0.9 wt% chopped brown fiber, and an additional 25.2 wt % Wyoming fly ash wereadded and mixed for 30 seconds. The resulting material had a resincontent of 36%, a ratio of rigid to rubbery polyol of 90%, a solidscontent of 64%, a 10% excess isocyanate content, and a fiber content of4.4%, all by weight based on the total composition unless notedotherwise. The resulting material was suitable for forming syntheticlumber boards.

For each of Examples 2 and 3, water was added in amounts shown below (inpercent based on total polyol added); physical properties of theresulting material were tested, and the results provided below. The 200lb impact test was conducted by having a 200 lb man jump on an 18 inchspan of synthetic lumber board 2×6 inches. supported above the groundfrom a height of about 1 ft in the air, and evaluating whether the boardbreaks. H₂O (% Break 100 psi Hardness Flexural Flexural 200 lb ofDensity Strength Deflection (Durometer Strength Modulus impact testExample polyol) (lb/ft³) (psi) (in) C) (psi) (psi) (P/f) 2 0.10 63 7300.15 62 3129 118,331 P 2 0.23 59 650 0.15 57 2786 118,331 P 2 0.40 47450 0.15 52 1929 118,331 F 3 0.10 63 810 0.15 62 3472 118,331 P

Example 4

Fiberglass rovings (Ahlstrom, 0.755 g/ft) or brown basalt rovings (0.193g/ft) were positioned in a 24 inch mold for 2×4 inch synthetic lumber,and stabilized to limit movement relative to the mold surface (about0.125 in. in from the mold surface) and to keep them taut. The rovingswere applied dry, coated and pre-cured with the synthetic lumbercomposition (minus ash and chopped glass), and wet with a mixture of 49wt % rigid polyol (MULTRANOL 4035), 0.098 wt % surfactant (DC-197), 0.20wt % amine catalyst (33LV), and 49.59 wt % isocyanate (Hehr 1468A).

To the mold was added a synthetic lumber mixture, formed by combining16.6 wt % rigid polyol (MULTRANOL 4035), 5.5 wt % flexible polyol(MULTRANOL 3900), 0.16 wt % surfactant (DC-197), 0.07 wt % water, 3.7 wt% pigments, 0.003 wt % organic tin catalyst (UL-28, Air Products), and0.1 wt % amine catalyst (33LV), and mixing for 1 minute, then adding26.4 wt % Wyoming fly ash, mixing for 1 minute, and finally adding 20.4wt % isocyanate (MRS4, Bayer), 1.1 wt % chopped brown fiber, 3.4 wt %chopped 0.25 in. fiberglass, and 22.5 wt % Wyoming fly ash, and mixingfor 30 seconds.

The physical properties of the resulting boards were assessed, and areindicated below. Control boards were also prepared to differentdensities, and their physical properties evaluated as well. The axiallyoriented rovings greatly increased flexural strength, with little addedweight. The rovings tend to have a more pronounced strengthening effectas the load on the material is increased. Flexural Flexural Number ofDensity Flexural Modulus @ 100 psi Modulus @ 200 psi Roving type rovingsRoving coating (lb/ft³) strength (psi) (Ksi) (Ksi)) Basalt 10 Dry 411191 73 53 Fiberglass 10 Pre-cured resin 58 4000 188 135 Fiberglass 10Dry 62 5714 339 169 Basalt 40 Dry 49 2465 96 101 Basalt 40 Dry 31 165062 165 Fiberglass 10 Dry 32 2717 37 57 Fiberglass 10 Wet 36 3533 77 93Fiberglass 5 Wet 36 2410 64 71 Fiberglass 15 Wet 38 4594 171 80Fiberglass 20 Wet 35 4356 84 80 None 55 1808 147 98 None 66 4724 121 100None 68 — 169 135 None 59 2568 70 84 None 45 1319 82 62 None 35 1174 5663 None 41 746 59 0

The synthetic lumber produced by the invention was found to have goodfire retardant properties, achieving a flame spread index of 25, and toproduce only small quantities of respirable particles of size less than10 μm when sawn. It provides excellent compressive strength, screw andnail holding properties, and density. Extruded composite of theinvention generally provides mechanical properties that are even betterthan those provided by molded composite.

1. A method of continuously forming a molded material comprising:forming a composite mixture in an extruder, wherein the compositemixture comprises: a monomeric or oligomeric poly or di-isocyanate; apolyol; about 45 to about 85 weight percent of inorganic particulatematerial; and a catalyst; extruding the mixture through a die; andmolding the mixture into a shaped article.
 2. The method of claim 1,wherein the shaped article is a building material.
 3. The method ofclaim 2, wherein the building material is lumber.
 4. The method of claim2, wherein the building material is roofing.
 5. The method of claim 2,wherein the building material is siding.
 6. The method of claim 1,wherein the molded material is a foamed material.
 7. The method of claim1, further comprising allowing an exothermic reaction to proceed in theextruded without forced cooling except to control a runaway exotherm. 8.A polymer matrix composite material, comprising: a polyurethane formedby reaction of a reaction mixture, comprising: one or more monomeric oroligomeric poly- or di-isocyanates; a polyol selected from the groupconsisting of polyether polyols and polyester polyols, about 45 to about85 wt % of an inorganic particulate material, based on the total weightof the composite material wherein the inorganic particulate materialcontains less than about 0.5 wt % of water.